The long ranges objective of the proposed research is to define the sources and role of androgens during mammalian development. The specific objectives of the proposed research are to: (1) define the nature and significance of the testosterone-binding proteins of the differentiating genital ducts and mesonophros. Emphasis is being placed on C19 steroid specificity, source and number of binding proteins (receptors vs. carrier), in vivo vs. in vitro androgen bindings, and change in characteristics with differentiation. (2) Study the effects of testes and androgenic steroids on protein synthesis in the developing male reproductive tract.